Apparatus for producing a spun yarn

ABSTRACT

For producing a yarn ( 4 ) spun from a loose fibre array ( 2 ) using a vortex flow an apparatus is used in which between a fibre supply duct ( 1 ) and a yarn take-off tube ( 5 ) a vortex chamber ( 3 ) is provided. Into the vortex chamber ( 3 ) a fluid is injected via tangentially oriented nozzles ( 6 ), which subsequently is drained via an exhaust duct ( 7 ). This apparatus comprises a wall limiting the vortex chamber downstream zone formed e.g. by a wall plate ( 20 ). This plate separates the vortex chamber ( 3 ) from the exhaust duct ( 7 ), but for completely draining the fluid is provided with a plurality of openings ( 21 ) extending to the exhaust duct ( 7 ). Owing to the functional separation of the vortex chamber ( 3 ) from the exhaust duct ( 7 ), in which the inventive apparatus differs from the state of the art, the fibre losses are reduced.

[0001] The present invention concerns an apparatus according to the introductory part of the independent patent claim. The apparatus serves for producing a yarn sun from a loose fibre array supplied to apparatus, in which arrangement the fibre array passes through a vortex chamber in which the fibres are subject to a vortex flow of a fluid owing to which they are spun into a yarn.

[0002] Spinning devices of the type mentioned above are known e.g. from U.S. Pat. No. 5,528,895 or U.S. Pat. No. 5,647,197 (both by Murata). These devices comprise a fibre supply duct and a yarn take-off duct, in which arrangement the outlet zone of the fibre supply duct is oriented essentially towards the inlet zone of the yarn take-off duct and the outlet opening of the fibre supply duct is arranged at a distance from the yarn take-off duct. In the zone of the outlet opening of the fibre supply duct furthermore a twist stop means (e.g. an eccentric edge over which the fibres are pulled, or a substantially concentric pin around which the fibres are guided) is provided.

[0003] The inlet zone of the yarn take-off duct normally is laid out as a slender spindle surrounded by an exhaust duct of essentially annular cross-section. The exhaust duct extends from the intermediate room laid out as a vortex chamber and extends substantially parallel to the yarn take-off duct. The vortex chamber in this arrangement is of essentially the same diameter as the inlet zone of the exhaust duct and is provided with nozzles directed tangentially into the chamber for injecting a fluid (e.g. air). The fluid injected into the vortex chamber is sucked off through the exhaust duct, in which arrangement the vortex flow generated in the vortex chamber around the yarn take-off duct (spindle) and into the exhaust duct. The vortex chamber and an inlet zone of the exhaust duct thus substantially form a functional unit serving for imparting twist. Also the yarn take-off duct, which can be designed rotatable if required, also can assist the twist imparting action, in which arrangement various means ensure that the fibres are pressed against the wall of the yarn take-off duct and thus are carried on more effectively.

[0004] The cross-sections of the fibre supply duct, the yarn take-off duct and of the exhaust duct are small compared to the mean length of the fibres processed. The length of the fibre supply duct is laid out in such a manner that at least part of the fibres the leading ends of which already have reached the zone of the yarn take-off duct still are held in the inlet zone of the fibre supply duct (e.g. between the delivery rolls of a drafting system arranged upstream from the fibre supply duct).

[0005] Fibres supplied to an apparatus as described briefly above on one hand are held in the fibre array, and from the outlet opening of the fibre supply duct are guided into the yarn take-off duct substantially without twist being imparted. On the other hand the fibres in the zone between the fibre supply duct and the yarn take-off duct are subject to the centrifugal influence of the vortex flow owing to which they are radially driven away from the inlet opening of the yarn take-off duct. Yarns produced using the method described thus present a core of fibres extending essentially in the longitudinal direction of the yarn or fibre portions without substantial twist, and an outer zone in which the fibres or fibre portions are wrapped around the core.

[0006] This yarn structure is generated, according to a model explanation, in that leading fibre ends, in particular of fibres the trailing ends of which are still held in the fibre supply duct, directly reach the yarn take-off duct, but that trailing fibre ends, in particular if they are no longer held in the inlet zone of the fibre supply duct, under the influence of the vortex flow are pulled out of the fibre array and are wrapped around the yarn being formed. It also can occur that leading fibre ends under the influence of the vortex flow are angled off from the fibre array while the trailing fibre end remains in the fibre array, which results in the formation of loops, which can be seen in the corresponding yarn.

[0007] In any case fibres, which are held at the same time in the yarn being generated and thus are pulled into the yarn take-off duct, and are subject also to the vortex flow, which accelerates them centrifugally, i.e. away from the inlet opening of the yarn take-off duct, and pulls them into the exhaust duct. The fibre portions pulled from the fibre array by the vortex flow form a fibre vortex merging into the inlet opening of the yarn take-off duct, the longer portions of which are wrapped spirally about the outside of the spindle-shaped inlet zone of the yarn take-off duct, and in this spiral are pulled towards the inlet opening of the yarn take-off duct against the force of the flow in the exhaust duct. Fibres of which neither the leading end nor the trailing end is pulled into the yarn being generated, and with a probability increasing the shorter the fibre length, are carried away through the exhaust duct and thus represent undesirable fibre losses.

[0008] The spinning method described, known as such, is characterised in that very high spinning speeds can be achieved (up to ten times higher than in ring spinning). On the other hand it proves difficult to prevent high fibre losses using this method, and to achieve a sufficiently high proportion of fibres in the twisted outer zone of the yarn cross-section.

[0009] It thus is the objective of the present invention to propose changes in the apparatus, using which the spinning method described above can be improved. The present invention thus aims at creating an apparatus for spinning using a vortex flow, application of which is to permit reduction of the fibre losses compared to the state of the art, the yarn quality remaining at least equal.

[0010] This objective is achieved using the apparatus defined in the patent claims.

[0011] The present invention is based on the idea that the vortex chamber and the exhaust duct be functionally separated in such a manner that the fibre vortex cannot extend indefinitely downstream into the exhaust duct, but remains limited to the vortex chamber, i.e. to a room functionally separated from the exhaust duct. This idea is realised in that the vortex chamber is limited by a wall, and that all the fluid is guided through this wall into the exhaust duct. At the centre of the wall forming a downstream limitation of the vortex chamber the inlet opening of the yarn take-off duct is arranged. The wall forming the downstream limitation of the vortex chamber does not exert any twist imparting function, i.e. it does not rotate. For draining the fluid openings are provided in this wall distributed around the yarn take-off duct merging into the one or a plurality of exhaust ducts, which openings also can be united into an annular opening.

[0012] Owing to the functional separation, briefly described above, of the vortex chamber and the exhaust duct, the probability of fibre losses via the exhaust duct is reduced. Fibres in the fibre vortex of which no ends are caught in the yarn being generated thus remain longer in the vortex chamber, and the probability, that they are carried on by the end portions of twirling fibres held in the yarn, increases. This effect reduces undesirably high fibre losses, which occur according to the state of the art.

[0013] Forms of realisation of the inventive apparatus for producing a yarn spun from a loose fibre array using a vortex flow are discussed in the following, in the sense of mere examples, in more detail with reference to the drawings. It is shown in the:

[0014]FIG. 1 The outlet zone of the fibre supply duct and the inlet zone of the yarn take-off duct (vortex chamber zone) of a known apparatus for producing a yarn spun from a loose fibre array using a vortex flow (shown in a section);

[0015]FIG. 2 The vortex chamber zone, also shown in a section, of an embodiment of the inventive apparatus in the sense of an example;

[0016]FIG. 3 The wall plate limiting the vortex chamber downstream, according to the FIG. 2, seen in a top view (line A-A in the FIG. 2);

[0017]FIG. 4 A further embodiment of the inventive apparatus (shown in the same manner as in the FIG. 2);

[0018]FIG. 5 The wall plate limiting the vortex chamber downstream, according to the FIG. 4 (line B-B in the FIG. 4);

[0019]FIGS. 6 and 7 The vortex chamber zone, shown in a sectional view, of two further embodiments of the inventive apparatus.

[0020] In the FIG. 1 the vortex chamber zone is shown of an apparatus according to the state of the art, using which in a vortex chamber 3 twist is imparted to a fibre array 2 supplied through a fibre supply duct 1 in such a manner that a yarn spun there from is generated in the vortex chamber 3 by injection of a fluid, e.g. air, via nozzles 6 tangentially merging into the chamber. The fluid is drained through an exhaust duct 7 presenting an annular cross-section surrounding the yarn take-off duct 5, the inlet opening zone of the exhaust duct 7 is of substantially the same diameter as the vortex chamber 3, is that the vortex flow generated in the vortex chamber 3 extends into the exhaust duct 7, and that fibre portions 8 pulled from the fibre array under the influence of the centrifugal effect of the vortex flow in the exhaust duct are wrapped spirally around the spindle-shaped inlet zone of the yarn take-off duct 5. The vortex chamber 3 and the inlet zone of the exhaust duct 7 thus form a functional unit in such a manner that fibres not caught in the yarn being generated with high probability are flushed by the fluid into the exhaust duct 7 and thus are lost for the yarn being produced.

[0021] At the outlet opening 9 of the fibre supply duct 1 in the embodiment shown an edge 10 is arranged as a twist stop, arranged eccentrically with respect to the yarn take-off duct 5. Also known is the application of a needle or pin arranged concentrically with the yarn take-off duct, which pin represents a temporary yarn core.

[0022] In the FIG. 2 a first embodiment of the inventive apparatus is shown in the sense of an example. As in the FIG. 1 the vortex chamber zone is shown in a sectional view, i.e. the outlet zone of the fibre supply duct 1 with the outlet opening 9 and the twist stop means 10 and the inlet opening of the yarn take-off duct 5 with its inlet opening 11, as well as the vortex chamber 3 and the exhaust duct 7, which as in the FIG. 1 presents e.g. an essentially annular cross-section.

[0023] Between the vortex chamber 3 and the exhaust duct 7 a circular disc type wall plate 20 is arranged supporting the inlet opening 11 of the yarn take-off duct 5 and is provided with a plurality of openings 21 distributed about this inlet opening 11, via which openings the fluid escapes from the vortex chamber 3 into the exhaust duct 7. Obviously the exhaust duct 7 presenting an annular cross-section also can be replaced by a plurality of exhaust ducts aligned to the coordinated openings 21.

[0024] The fibre portions 8 twirling over the wall plate 20, which are bound into the yarn being generated, cannot penetrate through the openings 21 but sweep across the openings. The fibre vortex thus is limited to the vortex chamber 3, and the fibres bound into the yarn can hold the fibres not bound into the yarn better in the twirling fibre array.

[0025] In order to limit the density of fibres present in the vortex chamber 3 and to prevent excessive fibre friction on the radial walls of the vortex chamber 3, it proves advantageous to increase the radius of the vortex chamber 3 with respect to the state of the art to at least one tenth (advantageously to more than one sixth) of the effective staple length of the fibres to be processed (the effective staple length being determined according to the formula published in the Japanese utility 2'513'582).

[0026] In order to reduce fibre friction on the wall plate 20 it proves advantageous to provide it with a friction-reducing surface structure (e.g. orange peel structure).

[0027] In the FIG. 3 a top view (seen in the direction A according to the FIG. 2) of the wall plate 20 is shown, which limits the vortex chamber 3 according to the FIG. 2 downstream zone towards the exhaust duct 7. The vortex direction of rotation is indicated by the arrows F. The openings 21 penetrate the wall plate 20 under an angle laid out in such a manner that the twirling fluid can escape into the exhaust duct without much change of direction and thus without generating turbulences.

[0028] The wall plate 20 shown planar parallel in the FIGS. 2 and 3 also can be shaped as a preferentially obtuse cone, the inlet opening 11 of the yarn take-off duct 5 being arranged on the top of the cone.

[0029] In the FIGS. 4 and 5 a further embodiment of the inventive apparatus is shown in the same manner as the arrangement according to the FIGS. 2 and 3, also in the sense of an example. Elements shown identically are designated using the same reference numbers as in the FIGS. 2 and 3.

[0030] The embodiment according to the FIGS. 4 and 5 differs in the design of the wall plate 20 the openings 21 of which are laid out as slots distributed along the circumference. The exhaust duct 7 again is shown presenting an annular cross-section; it could, however, be of another shape, suitably adapted to the slot-shaped openings 21.

[0031] In the FIGS. 6 and 7 two further embodiments, also shown in the sense of examples, of the inventive apparatus are shown in the same manner as the arrangements according to the FIGS. 2 and 4. In the embodiments shown here a central part of the wall limiting the vortex chamber downstream zone is formed by the front surface 30 of the yarn take-off duct 5. Adjacent to this central part a peripheral part is arranged the openings being arranged in the peripheral part (FIG. 6) or between the central and the peripheral part (FIG. 7).

[0032] In the FIG. 6 an embodiment is shown, in which the vortex chamber 3 does not extend essentially horizontally and at right angles to the yarn take-off duct 5, as shown in the FIGS. 2 and 4, but is substantially cone-shaped.

[0033] The central part of the wall limiting the vortex chamber downstream zone forms the face side surface of the inlet opening of the yarn take-off duct 5. Adjacent to this central part a peripheral part of this wall is formed by a perforated ring 31. The function of the exhaust duct 7 can be fulfilled e.g. by the airspace surrounding the apparatus.

[0034] In the FIG. 7 an embodiment is shown in which the wall limiting the vortex chamber downstream zone is formed by the face side surface of the inlet opening of the yarn take-off duct 5 and by a peripheral ring. The openings 21 extending to the exhaust duct 7 together form a single annular opening arranged between the central and the peripheral wall parts.

[0035] In order to ensure that the fibre portions 8 twirling in the fibre vortex cannot, or as few of them as possible, escape into the exhaust duct 7, which in the arrangement shown here again is laid out as narrow as possible and as close as possible near the inlet opening 11 of the yarn take-off duct 5. 

1. Apparatus for producing a yarn (4) spun from a loose fibre array (2) using a vortex flow acting as the sole twist-imparting means, which apparatus comprises a fibre supply duct (1), with an outlet opening (9), and a yarn take-off duct (5) with an inlet opening (11) distanced from said outlet opening (9), as well as means for generating a vortex flow in a vortex chamber (3), which essentially is arranged between said outlet opening (9) and said inlet opening (11), provided with nozzles (6) for injecting a fluid into the vortex chamber (3) and generating the vortex flow in the vortex chamber (3), and an exhaust duct (7) for draining the fluid from the vortex chamber (3), characterised in that the apparatus is provided with a wall limiting the vortex chamber (3) downstream zone, separating the vortex chamber (3) from the exhaust duct (7), at the centre of which said inlet opening (11) is arranged, and which for completely draining the fluid is provided with a plurality of openings (21) extending to the exhaust duct (7).
 2. Apparatus according to the claim 1, characterised in that the wall limiting the vortex chamber (3) downstream zone extends at right angles to the axis of the yarn take-off duct (5).
 3. Apparatus according to the claim 1, characterised in that the wall limiting the vortex chamber (3) downstream zone is an obtuse cone on the top of which said opening (11) is arranged.
 4. Apparatus according to the claims 1 through 3, characterised in that the wall limiting the vortex chamber (3) downstream zone presents a friction-reducing surface structure.
 5. Apparatus according to the claims 1 through 4, characterised in that the wall limiting the vortex chamber (3) downstream zone is formed by a wall plate (20).
 6. Apparatus according to the claims 1 through 5, characterised in that the wall plate (20) for draining the fluid is provided with a plurality of openings (21), which extend inclined in the direction of the vortex flow through the wall plate (20).
 7. Apparatus according to the claim 5, characterised in that the wall plate (20) for draining the fluid is provided with a plurality of slot-shaped openings (21) distributed along its circumference.
 8. Apparatus according to the claim 7, characterised in that the slot-shaped openings (21) extending inclined through the wall plate (20) in the direction of the vortex flow.
 9. Apparatus according to one of the claims 1 through 4, characterised in that a central part of the wall limiting the vortex chamber (3) downstream zone is formed by a face side surface (30) of the inlet opening yarn take-off duct (5).
 10. Apparatus according to the claim 9, characterised in that a peripheral part of the wall limiting the vortex chamber (3) downstream zone is formed by a perforated ring (31).
 11. Apparatus according to the claim 9, characterised in that between the central part of the wall limiting the vortex chamber (3) downstream zone and a peripheral part of this wall an annular opening extending to the exhaust duct (7) is provided. 